排序方式： 共有160条查询结果，搜索用时 250 毫秒
151.
水平轴海流能发电机叶片设计与性能分析 总被引：2，自引：1，他引：1
全球海洋蕴藏着丰富的海流能,合理利用海流能可以有效缓解能源危机。以额定工况下获能系数达到最大值为目标,利用叶素-动量理论设计了150 kW水平轴海流能发电机的叶片。使用叶素-动量理论结合普朗特修正和葛劳渥修正的方法,预测了海流机在不同尖速比以及不同桨距角下的水动力性能,分析了攻角和载荷沿着叶片径向的分布规律。使用CFD方法计算了海流机在不同尖速比下的水动力性能,并与理论方法的计算结果进行了比较。理论方法和CFD方法的结果均表明,所设计的海流机最大获能系数位于设计尖速比处,证明基于叶素-动量理论的水平轴海流机叶片设计方法是有效的。 相似文献
152.
液动锤射流元件喷嘴临界流速预测与验证 总被引：2，自引：0，他引：2
应用CFD动态分析技术,对SC71B型液动锤内部流场进行了仿真分析,结果表明,其射流元件临界流速为20.305～22.565 m/s,大大低于凭经验预测的40 m/s。为检验这一理论预测结果,对SC71B型液动锤射流元件临界流速进行了实验测定,为21.83 m/s,表明理论预测结果与实测结果高度吻合,证明了基于CFD动态分析的液动锤射流元件临界流速理论预测方法的可行性;同时通过理论分析和实测获得了至今为止液动锤射流元件临界流速的最低值,可为研制油气钻井用低速射流元件驱动控制的液动锤提供重要参考。 相似文献
153.
The flow around a cylinder, surface mounted or partly buried has been examined at Reynolds number of 1.3×104 and 2.6×104 by using the flow visualization method in the case of steady current. The lengths of the upstream and downstream separation regions were determined and the characteristics of the flow area were discussed for the cylinder having different burial depth to the diameter ratio (G/D). For comparsion, some numerical results obtained from the application of the FLUENT, computational fluid dynamics (CFD) software package have also been presented. Both experimental and numerical results indicated that the lengths of the separation regions near the upstream and downstream of the cylinder decreased with the increasing burial ratio (G/D=0, 0.20, 0.50). The results have significant implications both for the illustration of the potential for using CFD software and highlighting the need for data of two dimensional flow around the buried cylinder. 相似文献
154.
以全海深自主遥控水下机器人(AutonomousRemotely-operated Vehicle, ARV)为研究对象,针对全海深ARV的稳定航行和作业控制需求,借助潜艇标准运动方程建立直航动力学模型,还提出使用多元函数泰勒展开的方法建立独立的垂直运动动力学模型。其次,以节约计算机资源为目的,采用拟合优度分析、显著性检验和全局敏感性分析的方法剔除动力学模型中不重要的水动力系数项,得到简化的动力学模型。将初始和简化动力学方程的拟合结果与计算流体力学仿真(Computational Fluid Dynamics, CFD)计算结果进行对比分析,对比结果表明,全海深ARV直航和垂直运动动力学模型和简化动力学模型均是可靠的。 相似文献
155.
基于致动线模型的错列式两风机尾流场数值模拟 总被引：1，自引：1，他引：0
风电场中风机之间存在十分复杂尾流相互干扰现象,尾流相互干扰效应对风机的功率输出、叶片载荷等产生十分显著的影响。采用致动线模型以及计算流体力学方法,研究两风机之间的复杂尾流干扰效应。在保持两风机纵向间距一样的情况下,考虑两风机在不同横向间距下,数值模拟两风机的部分尾流相互干扰现象,分析两风机的气动功率输出特性、尾流速度变化特性、风轮平面附近轴向诱导因子分布特性,尾涡结构以及尾流干扰效应。数值模拟结果表明:在上下游风机在沿着流向方向距离保持不变的情况下,随着横向间距的变化,上下游风机的尾流存在十分复杂的尾流相互干扰效应,对下游风机的气动功率输出以及两风机风电场的整体流场产生了显著的影响。 相似文献
156.
Estimation and analysis of the uncertainty introduced by using a numerical model for the investigation and study of any type of flow problem have become common industry practice. Through understanding and evaluation of the uncertainty introduced by a numerical model, the accuracy and applicability of the model itself are evaluated. In this paper, the numerical uncertainty of a CFD-methodology developed to analyse the hydrodynamic performance of a collective and cyclic pitch propeller (CCPP) is estimated and analysed. The CCPP is a novel propulsion and manoeuvring concept for autonomous underwater vehicles, aimed to generate both propulsion and manoeuvring forces through advanced control of the propeller's blade pitch. The numerical uncertainty is established for three performance parameters, the generated propulsive force, the side-force magnitude, and the side-force orientation, by conducting a grid and time-step refinement study over three operational conditions. Additionally, the influence of the oscillatory uncertainty, introduced by the periodic nature of the problem, is investigated although shown to have a minimal effect when properly monitored. Based on a least-squares regression analysis of the refined simulation results, the numerical uncertainty is proven to be dominated by the introduced discretisation errors. In the case of the propulsive and side-force magnitude, the total uncertainty is dictated by the time discretisation uncertainty under bollard pull conditions, while the total uncertainty of the captive cases is mainly a result of the spatial discretisation uncertainty. The total uncertainty in the side-force orientation is observed to be primarily a consequence of the time discretisation uncertainty for all simulated cases. Overall, the total uncertainty for captive cases can be considered satisfactory for all three performance parameters, while further work is needed to reduce the observed uncertainty of the simulations under bollard pull conditions. 相似文献
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158.
Increasing propulsion efficiency, safety, comfort and operability are of the great importance, especially for small ships operating on windy sites like the North Sea and the Baltic Sea. Seakeeping performance of ships and offshore structures can be analysed by different methods and the one that is becoming increasingly important is CFD RANS. The recent development of simulation techniques together with rising HPC accessibility enables performance of advanced seakeeping simulations for ships in a full scale. The paper presents CFD seakeeping analysis for a case study vessel in two variants: V-shaped bulbous bow hull form (as built) and innovative hull form (X-bow type). The study presents the influence of redesigning the ship on selected seakeeping aspects. The advanced CFD model, with the application of overset mesh technique, was described in detail. Selected numerical results were validated on the basis of experimental testing in a towing tank and showed good agreement. The approach demonstrated here of performing the CFD seakeeping simulations for the analysis of ship performance in a full scale and close to real loading conditions has direct application to the design process as well as in determination of optimal operational parameters of any ship. 相似文献
159.
Computational Fluid Dynamics (CFD) numerical analysis was employed to analyze the situations tested experimentally, as described in Part I. The methodology and results of the CFD analyses are discussed and compared with the observations made from the experiments. The numerical model performed satisfactorily with regard to obtaining the impact forces exerted on the model pipe as well as simulating the hydroplaning phenomenon and estimating slurry flow heights. The experimental results were combined with the results of the CFD analyses to develop a practical method to compute the drag force caused by a submarine debris flow impact on a pipeline. The CFD analyses provided some insight to the separated region characterization, but the attempt to analyze the vortex shedding phenomenon as observed in the experiments was unsuccessful. Additional studies are required for better understanding of both the separated region characteristics and vortex shedding. 相似文献
160.
地表气温上升速度约为0.1 ℃/（10 a），然而受太阳辐射影响，地面气象站观测到的气温会高于真实大气温度，存在1 ℃量级的辐射误差。因此，本文提出了一种基于数据融合的铝壳温度传感器设计。首先，利用流体动力学方法计算温度传感器在不同环境条件下的辐射误差。其次，为获得连续辐射误差结果，利用神经网络算法对辐射误差数值计算结果进行学习，形成误差订正方程。最后，将太阳辐射误差订正方程修正值与试验结果进行对比。结果表明，基于数据融合的铝壳温度传感器可将辐射误差降至0.05 ℃以内。 相似文献